Studies in GEMM of PDA have demonstrated that tumor-derived GM-CSF promotes the development of a dense myeloid infiltrate that suppresses infiltration of T cells within the tumor microenvironment.[8], [9] These studies showed that human PDA also produces GM-CSF and one might envision a similar paucity of T cells in the tumor microenvironment. The gene discussed is CSF2; the disease is Patent ductus arteriosus.