A polypeptide is disclosed that is specifically detected in the cells of the prostate, termed Splice Variant-Novel Gene Expressed in Prostate (SV-NGEP). Polynucleotides encoding SV-NGEP are also disclosed, as are vectors including these polynucleotides. Host cells transformed with these polynucleotides are also disclosed. Antibodies and immunoconjugages are disclosed that specifically bind SV-NGEP. Methods are disclosed for using an NGEP polypeptide, an antibody that specifically binds SV-NGEP, or a polynucleotide encoding SV-NGEP. Assays are disclosed for the detection of prostate cancer. Pharmaceutical compositions including an SV-NGEP polypeptide, an antibody that specifically binds SV-NEGP, or a polynucleotide encoding SV-NGEP are also disclosed. These pharmaceutical compositions are of use in the treatment of prostate cancer.