CSF2 and neoplasm: Recombinant NDVs with an inserted GM-CSF gene increased the stimulation of human peripheral blood mononuclear cells (PBMC) by the infected tumor cells and led to a much higher IFN-α production in these cells compared to the control virus with no transgene, suggesting that GM-CSF-armed NDV could be a potential tumor immunotherapy to enhance immune cell infiltration [61].