Evaluation of therapeutic effects of natural killer (NK) cell‐based immunotherapy in mice using in vivo apoptosis bioimaging with a caspase‐3 sensor

ABSTRACT Natural killer (NK) cell‐based immunotherapy is a promising strategy for cancer treatment, and caspase‐3 is an important effector molecule in NK cell‐mediated apoptosis in cancers. Here, we evaluated the antitumor effects of NK cell‐based immunotherapy by serial noninvasive imaging of apoptosis using a caspase‐3 sensor in mice with human glioma xenografts. Human glioma cells expressing both a caspase‐3 sensor as a surrogate marker for caspase‐3 activation and Renilla luciferase (Rluc) as a surrogate marker for cell viability were established and referred to as D54‐CR cells. Human NK92 cells were used as effector cells. Treatment with NK92 cells resulted in a time‐ and effector number‐dependent increase in bioluminescence imaging (BLI) activity of the caspase‐3 sensor in D54‐CR cells in vitro. Caspase‐3 activation by NK92 treatment was blocked by Z‐VAD treatment in D54‐CR cells. Transfusion of NK92 cells induced an increase of the BLI signal by caspase‐3 activation in a dose‐ and time‐dependent manner in D54‐CR tumor‐bearing mice but not in PBS‐treated mice. Accordingly, sequential BLI with the Rluc reporter gene revealed marked retardation of tumor growth in the NK92‐treatment group but not in the PBS‐treatment group. These data suggest that noninvasive imaging of apoptosis with a caspase‐3 sensor can be used as an effective tool for evaluation of therapeutic efficacy as well as for optimization of NK cell‐based immunotherapy.—Lee, H. W., Singh, T. D., Lee, S.‐W., Ha, J.‐H., Rehemtulla, A., Ahn, B.‐C., Jeon, Y.‐H., Lee, J. Evaluation of therapeutic effects of natural killer (NK) cell‐based immunotherapy in mice using in vivo apoptosis bioimaging with a caspase‐3 sensor. FASEB J. 28, 2932–2941 (2014). www.fasebj.org