The present invention relates to a novel member of the NK family of homeobox genes. In particular, isolated nucleic acid molecules are provided encoding the human NK-3 prostate specific gene 1 (NKX3.1) protein. NKX3.1 polypeptides are also provided as are vectors, host cells and recombinant methods for producing the same. The invention further relates to screening methods for identifying agonists and antagonists of NKX3.1 activity. Also provided are diagnostic methods for detecting prostate cancer and other cancers and therapeutic methods for prostate cancer and other cancers.