CSF2 and cancer: Proof of principle studies have shown that “cold” to “hot” tumor conversion can be achieved, for example by intra-tumor delivery of oncolytic viruses such as Talimogene laherparpvec (T-VEC), an engineered herpes simplex virus which selectively infects cancer cells and expresses the dendritic cell attractant granulocyte-macrophage colony-stimulating factor (GM-CSF) (Johnson et al., 2015).