JX-594, the most famous oncolytic vaccinia virus carrying a human granulocyte-macrophage colony-stimulating factor (GM-CSF) gene with the thymidine kinase (TK) gene deletion, has been advanced to clinical phase III for the treatment of advanced hepatocellular carcinoma (HCC) and clinical phase II trial for renal cell carcinoma [13,14,15,16,17]. This evidence concerns the gene TKT and hepatocellular carcinoma.