The present invention relates to a new and potent tumor antigen capable of causing T cells to elicit an immune response and methods of its use in the detection, prevention, and treatment of cancer, preferably melanoma, in mammals. More specifically, this invention relates to the identification of a novel tyrosinase-related protein 2(TRP2), specifically TRP2-6b protein, and peptides derived from said protein. The present invention therefore also relates to nucleic acid seciuences that encode the TRP2-6b protein or peptide fragments thereof.