CSF2 and melanoma: Oncolytic viruses (OVs) are therapeutically useful viruses that preferentially infect and damage cancerous tissues without harming normal tissues.2 Genetically engineered human herpes simplex virus 1 (HSV-1) expressing granulocyte-macrophage colony-stimulating factor (GM-CSF; T-VEC, also known as OncoVEXGM-CSF) has been approved by the US Food and Drug Administration for use in melanoma patients.3 Oncolytic viro-immunotherapy is an attractive strategy for HCC.