TRAG-3, a novel cancer/testis antigen, is overexpressed in the majority of melanoma cell lines and malignant melanoma.

Background: We have identified a novel cancer/ testis antigen, TRAG-3, (Taxol Resistance Associated Gene-3) that was initially discovered in search for new genes involved in drug resistance by differential display. Early study of TRAG-3 revealed minimal to absent expression in various normal tissues and over-expression in many carcinoma cell lines including several melanoma lines. Materials and Methods: Northern and RT-PCR technologies were used to evaluate TRAG-3 expression in numerous cell lines and tumor tissue. Results: Analysis of a wider panel of normal tissues, 32 melanoma cell lines and 4 malignant melanomas demonstrates TRAG-3 expression in 25 of the 32 melanoma cell lines (78%) and four of four of the malignant melanoma tumors (100%). Of the additional eight normal tissues screened, expression was present in normal testis but absent in all other tissues. RT-PCR evaluation of TRAG-3 reveals two transcripts in many carcinoma cell lines with sequencing of these products demonstrating the 799 bp TRAG-3 transcript and a second alternatively spliced transcript, TRAG-3 long . TRAG-3 maps to band Xq28 within a MAGE gene complex, however sequence analysis demonstrates that TRAG-3 is not homologous to other known cancer/testis antigens. Conclusion: TRAG-3 appears to be a novel cancer/testis antigen.