Cell surface ROR1 expression was further confirmed by IHC using goat anti-human ROR1 pAbs on a formalin-fixed paraffin-embedded (FFPE) of pre-B-ALL cell line 697 with E2A-PBX1 genotype, whereas neither cell surface nor intracellular ROR1 expression was detectable in the cell line REH with TEL-AML1 genotype (Fig. 2D). Here, PBX1 is linked to acute lymphoblastic leukemia.