IRF4 and cancer: This cascade ultimately produces myeloid-specific transcription factors, including PU.1 and interferon regulatory factor 4 (IRF4).364,365 The critical role of GM-CSF in myeloid cells is demonstrated in GM-CSF-transgenic (Tg) mice, which exhibit significantly increased counts of myeloid subsets such as macrophages, neutrophils, and eosinophils compared to control mice.366,367 Furthermore, studies on GM-CSF-deficient (GMCSF−/−) mice reveal that while GM-CSF is essential for emergency myelopoiesis in response to infection, cancer, and stress, it is not required for basal myelopoiesis.368,369