Studies indicate that mutations in tumor suppressor genes occur early in the process of carcinogenesis, and that these mutations are correlated with a subsequent development of cancer. The detection of such alterations would provide useful molecular markers for diagnosis, surveillance, early tumor identification and intervention, and prognosis. A novel human gene, designated as “Zsig62,” resides within a region of chromosome 16q that is associated with prostate and breast cancer, and that appears to contain tumor suppressor genes. Like a tumor suppressor gene, the Zsig62 gene is expressed in particular normal tissues, but not in tumors derived from those tissues.