CD53 and Ewing sarcoma: STEAP1, a member of a family of metalloreductases described as a cell-surface antigen in prostate tissue [49, 50] and reported to be highly expressed in prostate, breast, bladder, colon ovarian carcinomas, in Ewing's sarcoma [51] and in endothelial cells in the vessels of human lung tumours [52], is highly upregulated in RA1, RB1, RB1.1 and RB2 erlotinib-resistant cell lines (Figure 8b, 8c).