uPAR levels as determined by ¹²⁵I-ATF receptor-binding assay. (A) HL60 GM-CSFR levels were determined by ¹²⁵I-GM-CSF receptor-binding assay. (B) uPAR expression levels of Sig M5. The x-axis represents the concentration of ¹²⁵I-ATF (pg/mL); the y-axis represents the amount of cell-bound ¹²⁵I-ATF (cpm). (C) uPAR levels expressed as number of receptors/cell in the 13 AML cell lines. DTU2GMCSF-resistant cells (black) have lower uPAR expression levels than DTU2GMCSF-sensitive cells (white, without the addition of pro-uPA; gray, requiring the addition of pro-uPA).