RAET1L and neoplasm: Cell surface expression of ULBP6 was confirmed on tumor cells after subcutaneous implantation into μMT−/− mice (used to minimize the immunogenicity of human ULBP6), and sULBP6 in mouse sera was within the range of sULBPs found in human plasma from patients with cancer (Supplementary Fig. S5A and S5B).