Interleukin-1 Receptor Accessory Protein (IL1RAP), encoded by the IL1RAP gene, is a receptor for interleukin-1.367,368 It has been identified as a CSC marker for myeloid leukemia.369 Similarly, CD25, a receptor for interleukin-2, and CD123, a receptor for interleukin-3, are also identified as CSC markers for AML or CML.370–373 CD70, expressed on the surface of various cells, and CD27, expressed on the T cell surface, are a pair of costimulatory molecules. The gene discussed is IL1RAP; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.