IL3 and chronic myelogenous leukemia, BCR-ABL1 positive: Fragment of Interleukin 3 The interleukin-3 (IL-3) fragment, a native ligand for the interleukin-3 receptor α, is overexpressed on chronic myelogenous leukemia (CML) blasts relative to normal hematopoietic cells, making it a viable target for cancer drug delivery systems [225,226].