A novel gene (designated 184P1E2) and its encoded protein, and variants thereof, are described wherein 184P1E2 exhibits tissue specific expression in normal adult tissue, and is aberrantly expressed in the cancers listed in Table I. Consequently, 184P1E2 provides a diagnostic, prognostic, prophylactic and/or therapeutic target for cancer. The 184P1E2 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 184P1E2 can be used in active or passive immunization.