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J. Exp. Med.,
Volume 188, Number 6, September 21, 1998 1005-1016
By



From the * Division of Experimental Oncology D, Istituto Nazionale Tumori, 20133 Milan, Italy;
and the We report here the identification of a new shared human melanoma antigen recognized by a
human leukocyte antigen (HLA)-A*68011-restricted cytotoxic T lymphocyte clone (CTL
128). The cDNA encoding this antigen is composed of a partially spliced form of the melanocyte differentiation antigen tyrosinase-related protein (TRP)-2, containing exons 1-4 with retention of intron 2 and part of intron 4 (TRP-2-INT2). The sequence coding for the antigenic
epitope is located at the 5' end of intron 2 and is available for translation in the same open
reading frame of the fully spliced TRP-2 mRNA. This peptide is also recognized by CTL 128 when presented by the HLA-A*3301, a member of the HLA-A3-like supertype that includes
the HLA-A*68011. Quantitative reverse transcription PCR analysis carried out on total and/or
cytoplasmic mRNA demonstrated that, in contrast to the fully spliced TRP-2 mRNA expressed in melanomas, normal skin melanocytes, and retina, the TRP-2-INT2 mRNA could
be detected at significant levels in melanomas but not in normal cells of the melanocytic lineage. Instead, in these normal samples, both the spliced and the unspliced transcript of gp100
were expressed at high levels. Absence of endogenous TRP-2-INT2 expression in melanocytes
was also confirmed by lack of recognition of HLA-A*68011-transduced, TRP-2+ melanocyte
lines by CTL 128. These results indicate that a partially spliced form of a differentiation antigen
mRNA, present in the cytoplasmic compartment of neoplastic but not normal cells of the melanocytic lineage, can be the source of a melanoma-restricted T cell epitope.
Gene Therapy Program, Istituto Scientifico San Raffaele Hospital, 20132 Milan, Italy
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