CD99 and Ewing sarcoma: Other genes typically expressed in Ewing sarcoma cells that remained stably expressed after transfection included the putative cancer/testis antigen LIPI (4, 5), LIPH (46), the surface glycoprotein CD99 (47), cyclin D1 [CCND1 (4, 48)], janus kinase 1 [JAK1 (4)], and the retinoic acid metabolizing cytochrome P450 member 26B1 [CYP26B1 (4, 49)] (Figure 3).