ULBP2 and cancer: Finally, by using the pCMVExt-Fc vector, we expressed two challenging proteins, the human ROR1-ED that is involved in cancer progression of a number of blood and solid malignancies (Hojjat-Farsangi et al., 2014) and the ligand for the NKG2D activating receptor on the surface of NK cells, ULBP2 (Sutherland et al., 2006).