LIPI and cancer: Due to the absence or low expression in adult somatic tissues, cancer/ testis antigens are considered as potential targets for T cell priming in ES, which include phosphatidic acid specific membrane-associated phospholipase A1 beta (lipase I, LIPI), X antigen family member 1 (XAGE1) and New York esophageal squamous cell carcinoma 1 (NY-ESO-1, also known as CTAG1).