To overcome the limitations associated with optical imaging, as well as antibody-mediated imaging probes (22), our group labeled a cCPE.GST conjugate with the γ-emitting radioisotope 111In (half-life, 2.8 d) to enable noninvasive whole-body claudin-4 detection in breast cancer mouse models by SPECT imaging. Here, CLDN4 is linked to breast cancer.