This impressive capacity in spreading through tumor tissue, which was reflected by our observation that VSV-CD133 was also efficacious when injected intravenously, can be regarded as important property to reach and destroy CSCs in a clinical situation of HCC, where CD133-positive CSCs make up a low percentage of all cells present in tumor tissue (4, 41). This evidence concerns the gene PROM1 and hepatocellular carcinoma.