Increased tumor cell expression or elevated serum activity of APN/CD13 has been associated with poor prognosis in, e.g., pancreatic, hepatocellular [9], non-small cell lung cancer [6], breast cancer [61], Philadelphia chromosome-negative B-cell acute lymphoblastic leukemia [62], and multiple myeloma [7]. Here, ANPEP is linked to B-cell acute lymphoblastic leukemia.