TKT and cancer: Since the first report of a thymidine kinase (TK) deleted herpes simplex virus (HSV) in cancer treatment [32], more than 10 families of oncolytic viruses have entered clinical trials, including adenovirus, coxsackie virus, herpes simplex virus, measles virus, new castle disease virus, parvovirus, poliovirus, reovirus, and vesicular stomatitis virus [33].