A novel gene 254P1D6B and its encoded protein, and variants thereof, are described wherein 254P1D6B exhibits tissue specific expression in normal adult tissue, and is aberrantly expressed in the cancers listed in Table I. Consequently, 254P1D6B provides a diagnostic, prognostic, prophylactic and/or therapeutic target for cancer. The 254P1D6B gene or fragment thereof, or its encoded protein, or variants thereof, or a fragment thereof, can be used to elicit a humoral or cellular immune response; antibodies or T cells reactive with 254P1D6B can be used in active or passive immunization.