3 We focus here on 1 differentially expressed EST (GenBank accession no. In a previous study, we determined differences in gene expression by comparing a poorly versus a highly metastatic human melanoma cell line, 1F6 and Mel57, respectively, by using high-density oligonucleotide arrays. Screening for genetic alterations that are necessary for a tumor to develop and metastasize may give more insight into the process of tumor progression and may lead to the identification of new diagnostic markers and/or targets for (immuno-) therapy. 2 The only successful treatment for malignant melanoma nowadays is resection of the lesion at an early stage. In addition to its highly increasing incidence because of environmental changes, 1 malignant melanoma is also aggressive due to its high capability of dissemination in early stages of tumor progression. Malignant melanoma is a serious type of cancer derived from the melanocytic cell lineage. © 2002 Wiley-Liss, Inc.ĪN, atypical nevus CTA, cancer/testis antigen EST, expressed sequence tag MM, melanoma metastasis MMA-1, malignant melanoma associated-1 NN: nevus nevocellularis PM, primary melanoma. We conclude that MMA-1a and MMA-1b are new members of the family of cancer/testis antigens. Expression of MMA-1a and/or MMA-1b was also identified in other tumor cell lines and fresh tumor samples of variable origin, e.g., lung, liver, bladder and soft tissues (sarcomas). During melanocytic tumor progression, MMA-1a and/or MMA-1b exhibited an emergence of expression in primary melanoma (20%) and melanoma metastasis samples (30%) after only 1 round of PCR. Even more sensitive screening achieved by performing multiple semi-nested RT-PCR showed no or very low expression in the other normal tissues tested. Among 30 different normal tissue samples, expression of MMA-1a and MMA-1b was exclusively found in the testis after a first PCR of 30 cycles. Expression profiles of MMA-1a and MMA-1b are determined by reverse transciptase polymerase chain reaction (RT-PCR) analysis. Homology search displayed a splice variant of MMA-1a that lacks exon 3 and that was called MMA-1b. The MMA-1a gene is localized on chromosome 21q22.2 and its mRNA exists of 4 exons. We identified an expressed sequence tag (EST), which we called malignant melanoma-associated 1 (MMA-1a), showing evident differential expression between the 2 cell lines. Using high-density oligonucleotide array analysis, we have recently compared the gene expression profiles of 2 human melanoma cell lines with marked difference in metastatic behavior after subcutaneous inoculation into nude mice (de Wit et al., Melanoma Res, in press).
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