A novel gene (designated 101P3A11 or PHOR-1) and its encoded protein, and variants thereof, are described wherein 101P3A11 exhibits tissue specific expression in normal adult tissue, and is aberrantly expressed in the cancers listed in Table I. Consequently, 101P3A11 provides a diagnostic, prognostic, prophylactic and/or therapeutic target for cancer. The 101P3A11 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 101P3A11 can be used in active or passive immunization.