TKT and glioblastoma: The first case using HSV-1 tk reporter gene imaging to visualize administered CAR-T cells was of a 57-year-old man with grade IV glioblastoma multiforme (NCT00730613), reported by Yaghoubi et al. 64 After gross tumor resection, a cumulative dose of 1 × 109 therapeutic T cells (expressing HSV1-tk as the reporter gene, and interleukin 13 [IL-13] zetakine targeting for IL-13Ra2-expressing tumor) into the tumor site.