SSX expression and function in prostate cancer

Background Cancer-testis antigens (CTAs) are a group of proteins whose expression is essentially restricted to testis germline cells among normal somatic cells. CTAs also possess a heightened expression in many different types of cancer. Due to their restricted expression in tumor cells among MHC class I-expressing cells, there has been interest in the CTA as essentially tumor-specific targets for CD8+ T cell-directed therapies. Amongst the CTA genes is the Synovial Sarcoma X chromosome breakpoint (SSX) gene family. There are ten members of the SSX family with a high degree of homology amongst them. SSX-2 is the most commonly expressed member of the SSX family, and serves as a prototypical member for study. We have previously demonstrated that SSX-2 expression is confined to metastatic tissue, and is not detected in primary prostate tumors. The function of the SSX family is largely unknown, and further insights into its function may reveal avenues for future directed therapies.