We have identified a gene located on chromosomes 21 that is expressed in normal and neoplastic prostate, and in normal testis, ovary, and placenta. We name this gene POTE (expressed in prostate, ovary, testis, and placenta). The POTE gene has 11 exons and 10 introns and spans ≈32 kb of chromosome 21q11.2 region. The 1.83-kb mRNA of POTE encodes a protein of 66 kDa. Ten paralogs of the gene have been found dispersed among eight different chromosomes (2, 8, 13, 14, 15, 18, 21, and 22) with preservation of ORFs and splice junctions. The synonymous:nonsynonymous ratio indicates that the genes were duplicated rather recently but are diverging at a rate faster than the average for other paralogous genes. In prostate and in testis, at least five different paralogs are expressed. In situ hybridization shows that POTE is expressed in basal and terminal cells of normal prostate epithelium. It is also expressed in some prostate cancers and in the LnCAP prostate cancer cell line. The POTE protein contains seven ankyrin repeats between amino acids 140 and 380. Expression of POTE in prostate cancer and its undetectable expression in normal essential tissues make POTE a candidate for the immunotherapy of prostate cancer. The existence of a large number of closely related but rapidly diverging members, their location on multiple chromosomes and their limited expression pattern suggest an important role for the POTE gene family in reproductive processes.

We identified a gene (NGEP) that is expressed only in prostate cancer and normal prostate. The two NGEP transcripts are 0.9 kb and 3.5 kb in size and are generated by a differential splicing event. The short variant (NGEP-S) is derived from four exons and encodes a 20-kDa intracellular protein. The long form (NGEP-L) is derived from 18 exons and encodes a 95-kDa protein that is predicted to contain seven-membrane-spanning regions. In situ hybridization shows that NGEP mRNA is localized in epithelial cells of normal prostate and prostate cancers. Immunocytochemical analysis of cells transfected with NGEP cDNAs containing a Myc epitope tag at the carboxyl terminus shows that the protein encoded by the short transcript is localized in the cytoplasm, whereas the protein encoded by the long transcript is present on the plasma membrane. Because of its selective expression in prostate cancer and its presence on the cell surface, NGEP-L is a promising target for the antibody-based therapies of prostate cancer.