A novel gene (designated 205P1B5) and its encoded protein are described. While 205P1B5 exhibits tissue specific expression in normal adult tissue, it is aberrantly expressed in prostrate cancer. Consequently, 205P1B5 provides a diagnostic, prognostic, prophylactic and/or therapeutic target for cancer. The 205P1B5 gene or fragment thereof, or its encoded protein or a fragment thereof, can be used to elicit an immune response.