This screen not only confirmed the known positive regulators of primitive CML expansion (e.g., IL-3, IL-1α/β, GM-CSF, IL-6, and IFN-γ), but also identified several new regulators, including myostatin propeptide (MSTNpp) [105]. The gene discussed is IL1A; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.