The protein encoded by this gene is an antigen that is overexpressed in many cancers but that is also expressed in normal testis. This gene is found in a duplicated region of the X-chromosome and therefore has a neighboring gene of identical sequence. Expressed in testis and ovary and in a wide variety of cancers. Detected in uterine myometrium. Expressed from 18 weeks until birth in human fetal testis. In the adult testis, is strongly expressed in spermatogonia and in primary spermatocytes, but not in post-meiotic cells or in testicular somatic cells (at protein level).