Figure 5.

CAR-T cellular visualization based on hNIS reporter SPECT/CT imaging. A. ^99mTcO₄^- SPECT images of low tumor burden mice (imaged 7 d post tumor inoculation). Mice with PC-LN3-PSMA (PLP) cell subcutaneous xenograft were treated with control CAR-T (4PTrN⁺, upper row) cells and PSMA-targeting CAR-T (4P28ζN⁺, lower row) cells. No visible activity was detected in the tumors of all of the three control mice on the day 4 p.t and day 9 p.t, and only one had subtle activity in the tumor on the day 14 p.t. Although there is no detailed description in the original reference, the accumulation in the tumor (yellow arrows) of rightmost mouse on day 14 p.t might be due to the non-specific infiltration of T cells into tumor tissue ¹⁰⁴. In comparison, significant SPECT signal was detected in the tumor of the mice treated with 4P28ζN⁺ CAR-T cells on day 9 p.t, and then the signal decreased on day 14 p.t as the tumor regression. B. ^99mTcO₄^- SPECT images of high tumor burden mice (imaged 14 d post tumor inoculation). Mice with PC-LN3(PL) cell xenograft (upper row) and PC-LN3-PSMA (PLP) cell xenograft (lower row) received 4P28ζN⁺ CAR-T cell infusion. Only subtle activity was detected on day 7 p.t in the PL tumors, indicating only a few CAR-T cells infiltration. In contrast, obvious SPECT signal was noted in the PLP tumors as early as day 1 p.t, which enhanced constantly till day 7 p.t (†=dead mouse). Adapted with permission from ⁵⁸, copyright 2018 Springer Nature.